it sounds like a logistical mistake to me. yes, it can be tested, hence my simpson 260 comment. do you have an ohmeter? or the knowlege to operate one? if not, you could take it to anyone with the smallest amount of electrical know-how and you could figure it out.

Mainly just look at what the guy in the picture is doing and know that it's going to show you DC resistance which is about 75% of AC resistance. So if this is an 8 ohm cab it'll show about 6 ohms on the screen when set to the "continuity" setting.

Go to Radio Shack, get a cheap multimeter ($14 or so), use it to check the cab, then return the meter. If its an 8 ohm cab, the meter will show around 6 ohms. If its a 4 ohm cab, expect a reading around 3.